Papers by Keyword: Giant Dielectric Constant

Abstract: ts well known that CaCu₃Ti₄O₁₂ (CCTO) ceramic presents high dielectric constants, which makes it a strong candidate to be used in microelectronic devices. Several routes were proposed to obtain CCTO crystalline phase, influencing in microstructure and sintering conditions of the ceramics. In this study CCTO powders were produced by a new chemical route, providing reduction on hold time and sintering temperature. Furthermore, the sintering was performed in conventional and microwave oven that produced different microstructures. In this way, the microstructure and dielectric properties of these ceramics were evaluated and compared, showing the higher values of dielectric constant due to lower grain size and reduced copper-rich phase on grain boundary presented by microwave sintered ceramics.

Abstract: CaCu3(Ti1-xZrx)O12 ceramics (x = 0.02, 0.04, 0.06, 0.08) were prepared by the conventional solid-state reaction method. Phase compositions, microstructure and dielectric properties were examined by XRD, SEM and impedance spectroscopy, respectively. The experimental results indicated that there is no obvious effect on microstructure characteristic by substituting Zr4+ for Ti4+. It was found that the values of the dielectric constant for all of the samples dropped into the order of 102, which is significantly lower than the order of 105 that of normally reported in the literature. It was suggested that the presence of impurity phases played an important role for the degeneracy of dielectric properties.

Abstract: CaCu3Ti4O12 (CCTO) ceramics were prepared by cold isostatic press (CIP) forming combined with the conventional sintering method. The effects of calcining temperature on properties of CCTO ceramics were investigated. The dielectric properties as the function of temperature at typical frequencies were measured in the temperature range from 243 to 363 K. In addition, the dielectric properties and complex impedances at room temperature were analyzed in a frequency range from 20 Hz to 106 Hz. The results showed that CCTO ceramics with dielectric constant higher than 104 were obtained. Compared with the dry press forming, CCTO ceramics prepared by CIP had more homogeneous grains, less porosity and better dielectric properties.